The invention relates to a high pressure gas discharge lamp comprising a ceramic discharge vessel having a container wall enclosing a discharge space having a filling, further comprising a first and a second electrode, mutually oppositely arranged in the discharge space and defining a length axis of the discharge vessel, still further comprising a first and a second feedthrough, both extending in a gas-tightly sealed manner through the container wall and on which feedthroughs a respective electrode is mounted, and further comprising a UV-enhancer.
The invention further relates to a method of manufacture of said electric lamp.
A lamp of the type mentioned in the opening paragraph is known from U.S. Pat. No. 5,811,933. The known lamp is a high-pressure discharge lamp, more in particular a metal halide lamp. Such a lamp is suitable for various applications such as general interior lighting, general exterior lighting, video illumination, etc. The discharge vessel of the known lamp is made of ceramic material and is often obtained, via an extrusion process, in a tubular shape and subsequently provided with end plugs/end parts. Alternatively a slip-casting process or an injection molding process is used to manufacture the discharge vessel with end parts. Ceramic material in the present description and claims is understood to be a densely sintered polycrystalline metal oxide such as, for example, Al2O3 or YAG, and densely sintered polycrystalline metal nitride such as, for example, AlN.
A known problem of this type of lamp is the comparatively wide spread in ignition time. This points to a shortage of free electrons during lamp ignition. The addition of a small quantity of 85Kr in the discharge vessel can supplement such a shortage. A disadvantage of this, however, is that 85Kr is radioactive. Efforts have been made to avoid this through the use of a UV-enhancer, which is a small UV discharge tube positioned adjacent the discharge vessel and acting as a UV source. The UV-enhancer in the known lamp is formed by a UV-transmitting ceramic tube positioned parallel to and at a distance from the discharge vessel. Upon breakdown, the UV-enhancer will generate said UV-radiation. The influence of this UV-radiation leads to the production of free electrons in the discharge vessel, which in turn strongly promote lamp ignition. Disadvantages of the known lamp are the relatively complicated construction, and the relatively cumbersome manufacture process which, in addition, is relatively expensive.